INDUSTRIAL A N D ENGINEERING CHEMISTRY
September, 1923
the others, showing just a little less bicarbonate removed than any of the others, which was probably due to changes in the water after the samples were collected. As a theoretical check on the analytical results of bicarbonate determinations in dea6rated water, the following formula, as given by Massink and H e y m q 4 was used to calculate the bicarbonate content: H+ = 6 X
X
961
present in either case as would be equivalent'to the amount of bicarbonate found, showing that part of the bicarbonate is combined with other elements, probably magnesium.
Bicarbonate CO, Carbonate CO,
Hf being the hydrogen-ion concentration and the COz values being expressed in milligrams per liter. A comparison of the calculated results with the experimental results on the different samples in Table I1 are given in Table 111. TABLE111-BICARBONATE EXPERIMENTAL CALCULATED 48.3 50.1 53.5 57.6 4.5 2 ...~
48.1
52.4 48.4 50.8
49.3 80.4 47.0
C02-MG. PER LITER EXPERIMENTAL CALCULATED 42.5 45.2 53.4 59.2 55.5 53.6
56.9 58.5
60.1 62.1
The results check fairly well, considering how much the value of the formula depends upon the accuracy of the pH measurements. The results on calcium in raw and deaerated water show that an appreciable amount is removed by deaeration-not as much, however, as would be expected from the amount of bicarbonate removed. Indeed, there is not as much calcium 4
J . A m . Water Works Assoc., 8,239 (1921).
W
S
F€R MIWON BhMBONWE COz
FIG 1
To give an idea of the relative amounts of bicarbonate removed, a curve is given showing the total bicarbonate present in the raw water, plotted against the per cent removal by deaeration. The per cent removal is found to increase slightly with increase in concentration. It would be interesting to test the effect of deaeration on water with higher bicarbonate content, but it could not be done by the writer, as the laboratory was only convenient to the one power plant where deaerated water was auailable.
Substitution and Addition of Chlorine to t h e Rubber Molecule' By J. McGavack UNITEDSTATICSRUBBERCo., NEW YORK,N Y.
T
The main points in this brief paper are that substitution occurs work done by Peachy.3 HE nature of the refirst in an uncontrolled temperature reaction of chlorine with rubber: In general, d authorities action of chlorine that, practically, substitution is complete before any addition occurs; PracticauY agree, with the with hydrocarbons that the procedure giues a quick method by which the rate of the chloexception of Boswell, that depends upon the temperature, light, and mechanrination of rubber may be determined at any particular time. the rubber hydrocarbon is ical conditions, as well as an unsaturated aggregaupon the nature of the tion of carbon and hydrohydrocarbon itself. Saturated hydrocarbons can only react gen. Boswell4 claims that, instead of having a number with chlorine by substitution. On the other hand, both of double bonds affording an opportunity for the addition substitution or addition may occur in the case of un- of compounds like bromine and chlorine, we have internal saturated hydrocarbons. For instance, the chlorination of linkages between the carbon atoms, thus causing complete toluene may result in entirely different chemical individuals, saturation, and that the formation of double bonds of free depending upon whether the reaction occurs in sunlight, valencies is only brought about when extreme or drastic diffused light, or a t an elevated temperature. In the same treatment is employed. I n any case, it was thought demanner the chlorinated products of ethylene may vary over sirable to study this reaction from the dynamic standpoint. a wide range, depending Primarily upon the Conditions under The method (Fig. 1) consisted in passing a definite quantity which the reaction is carried out. In fact, examples of this of chlorine measured by a flowmeter (1) through a cylindrical type are SO frequent and familiar that it is USeleSS to cite vessel exposed to diffused light containing a known quantity further cases. of rubber cement., The effluent gases were cooled by means For this TeaSon it Was thought that 2, dynamic study of of a condenser allowing the solvent to return to the reaction the chlorination of the rubber hydrocarbon should be inter- chamber and were measured by means of flowmeter (2). esting and perhaps indicate the preference for substitution These gases were then washed thoroughly with water to O r addition. Previous workers, such as Cklstone and remove any hydrochloric acid formed, measured by another Hibbert,2 have considered the chlorinated product of the flowmeter (3) ; and finally passed through strong alkali to mbber hydrocarbon from the end Point O n l y , and apparently absorb the final traces of chlorine. In this manner, by a have not dissected the reaction. The same is true of the simple glance at the flowmeter readings exactly what was 1 Presented before the Division of Rubber Chemistry at the 65th OCCUrring at any particdar moment Of the reaction could be Meeting of the American Chemical Society, New Haven, Conn., April 2 to 7, 1923. 2 J. Chew. SOC.(London), 63, 686 (1888).
Y
4
J SOL.Chem. I n d , S9, 55 (1918). India Rubber J., 64, 981 (1922).
INDUSTRIAL A N D ENGINEERING CHEMISTRY
902
determined. Far instance, Flowmeter 1 measured the initial quantity of chlorine; Flowmeter 2, the chlorine unabsorbed plus hydrochloric acid given off by the reaction; and Flowmeter 3, the unabsorbed chlorine. By substracting the readings of 3 from those of 2 we would have the amount of hydrochloric acid given off a t any particular time. Dividing this value by two, we would obtain the amount of chlorine substituted. The difference between the chlorine in and the chlorine out minus that substituted, of course, would give the value added.
acid given off is accurate to within the limits of the flowmeter readings. It can easily be seen from this graph that substitution occurs during Zhe first course of this reaction practically to the exclusion of addition. As the reaction proceeds the temperature decreases, substitution diminishes, and addition increases. This is also shown in Table I, which gives the results of nine experiments carried out in this manner. TABLEI HCI Rate of Given Off Pale Time Chlorine C c . a t Crepe Solof Run Cc./ Expt. 25O C. G. vent Min. Min. 35 CHCla 140 3 19,000 580 4 18,740 35 CHCla 250 280 35 CHCla 5 19,115 280 280 60 20,000 35 CHCla 385 '280 15 19,500 35 CHCla 195 500 16 19,035 35 C3€I;: Cat- 100 500
17
26 12 Q
FIG.1-CHLORINATIONAPPARATUS
It is to be remembered that in such a process the results will vary as much as 3 per cent, inasmuch as flowmeters for measuring gases are probably only accurate to this degree. Furthermore, it should be stated that absorption of chlorine by the water-gas bottles was not taken into consideration, but it was thought sufficient to saturate first with chlorine the water thus used. Experiment 17 gives a graphical representation of a typical experiment carried out in the manner described above. I n this graph the gas volumes are plotted as ordinates against time as abscissas. Here we have a graphical record of the three different flowmeter readings, the area of which can either be integrated or calculated by inspection. Thus, that area between 1 and 2 gives the amount of chlorine absorbed; that between 2 and 3, the volume of hydrochloric acid given off, or twice the volume of chlorine substituted; while that between 3 and the abscissas gives the amount of chlorine lost. Unfortunately, the last area is inaccurate 60
50
40
E
$-
30
2
20
10
20
40
60
80
100
120
140
I60
FIG.2
owing to the fluctuation of the temperature which allows for more or less absorption of chlorine by the solvent. On the other hand, that area representing the amount of hydrochloric
Vol. 15, No. 9
Ratio Chlorine HC1 to Final Temp. Rubber Product Range in Mols % ' 'C. 65.1 51 t o 2 5 2.98 2.96 65.04 47 t o 2 3 2.99 65.45 4 8 t o 2 3 64.55 30 t o 6 3.11 3.03 62.5 51to23 2.97 54to30
20,700 35 C?C; 160 500 3.22 19,210 35 CHCls 155 500 2.99 12,700 35 CC14 265 500 1.98 Reaction chamber surrounded by an ice bath.
... ...
62.9
60.0
54 t o 3 0 52to23 61to20
It can be seen from a glance a t Column 7, that the ratio of hydrochloric acid given off to the original amount of rubber when expressed in mols is approximately 3. This holds for all experiments, except Experiment 12, where this ratio is considerably less. This discrepancy is explained from the fact that with this experiment carbon tetrachloride in place of chloroform was used as a solvent. It is known that the solubility of the hydrochloride of rubber is approximately zero in this solvent, and hence what probably occurs in this case is, first, the addition of hydrochloric acid gas to the rubber molecule, precipitating a film of the hydrochloride on the rubber and thus preventing chlorination unless some mechanical stirring device is used. This reaction requires more detail than can be given in this brief note. It will also be seen fromColumn 8 that the percentage of chlorine in the final product is 65. If the chlorinated product does contain three atoms of substituted chlorine and four atoms of added chlorine, then the percentage of chlorine should be 65.1, which is in fair agreement with the experimental data. It may be seen also that the temperature was uncontrolled and that where the greatest substitution occurred there was the highest temperature. This is in agreement with known facts in regard to substitution and addition of halogens in hydrocarbons. International Conference on Standardization A conference of the secretaries of national industrial standardizing bodies was held in Zurich and Baden, Switzerland, July 3 to 7. Thirteen countries were represented, including all the more important industrial nations of Europe and America, P. G. Agnew being the delegate from the United States. A leading topic discussed by the conference was the interchange of information between the various national bodies during the development of the work in the different countries. At the first conference, held in London two years ago, arrangements were made for the systematic interchange of completed work, and, to some extent, of information on work in progress. While it was not possible to overcome all the difficulties existing by virtue of the important industrial considerations involved, very substantial progress was made. It is believed that the steps taken will lead immediately to a substantially increased amount of interchange of information during the earlier stages of standardization work, and that the way has been paved for a much more extensive interchange in the future. Provision was made for continuing the work of the conference on the many administrative problems of common interest, through a loose-knit continuing organization. An example of such work planned by the conference is the translation of technical terms of special importance or difficulty in standardization work. There will gradually be built up such a vocabulary of technical terms, mainly in English, French, and German, but supplemented as far as may be feasible and necessary by the corresponding terms in other languages.
